In recent years, asynchronous circuits have been used in many fields due to their advantages over synchronous circuits, such as lower power consumption, higher-speed operation, and lower electromagnetic radiation. Since asynchronous circuits involve no timing signals, delay control is extremely important.
A universal asynchronous receiver-transmitter (UART) is provided with a photocoupler between a transmitter and a receiver to perform switching operation on a pulse signal outputted from the transmitter. The photocoupler functions as a delay unit to delay a pulse signal. Unlike wiring, cables, and the like that transfer pulse signals, the photocoupler may delay the rising edge or falling edge of a pulse signal.
Such a delay in a pulse signal hinders normal data transmission and reception between the transmitter and the receiver. Therefore, it is difficult to perform normal data transmission and reception.